A noun in the Gnomish Lexicon of the 1910s glossed “mine” with variants gerdolm and gerdholm, a combination of G. groth “ore” and G. dolm “pit” (GL/38).
Gnomish
heb
preposition. round about, around
hebringli
place name. Hebringli
heb-
verb. to bind, bind round
heborodin
place name. Encircling Hills
hebrim
noun. bound(ary)
hebwirol
adjective. circumspect
hebon
adjective. bound; (also) bounded, surrounded
gerd(h)olm
noun. mine
gersauth
noun. mine
gersoth
noun. mine
habin
noun. shoe
In the earliest Lost Tales, the mountains around Gondolin, in later writings named Echoriath.